It is known that environmental experts are increasingly aware of the growing quantities of refuse at both municipal and parish level, as well as from industry. Large and modern refuse elimination plants, by virtue of circumstances, can only convert waste into another form even though the latter may occupy less volume than the starting material.
Also the situation in the case of stocks of raw materials in world economy have resulted in the knowledge that it is essential to strive for better utilization of available raw materials, manufacturing residues and waste. Desirable, therefore, would be an apparatus for comminuting heterogeneous materials, e.g. household and industrial refuse, occurring in large quantities, even when supplied in sacks, and of the high grade materials contained in this refuse, such as paper or packaging materials of all kinds, textiles materials, etc. After their comminution, such materials could be fed to other further processing stages, but a necessary condition is a suitable pulverising apparatus.
A further problem exists in the paper and woodfiber board producing industry: timber production is incapable of coping with the rapidly increasing consumption of paper. Therefore, it seems important to be able to process tree residues such as branch and root timber and also bark, hitherto unused, in the aforesaid industry for the production of papers, fibreboard and insulating board.
Known methods are scarcely capable of processing elastic, viscous, moist, sticky or bulky materials. At least, no efficient and competitively priced machine is available for a rational pulverising of such materials.
The incineration plants often used have the great disadvantage of leaving about 35 to 50% by weight of residue, even though the volume shrinks to about 1/10th that of the starting material.
The depositing of these residues without adversely affecting the nature of the ground-water is a difficult problem. Also contamination of the air by combustion gases creates difficulties. Only very expensive purification plants can either purify the waste gases and carry away the poison in liquid form, jeopardizing the ground-water, and also this is frequently undesirable.
Furthermore, it must be remembered that, for example, refuse contains large quantities of metal and in any rational pulverizing of such mass materials, it is particularly essential to use a high rate of throughput of the pulverizing machines, with economical power consumption and a low rate of wear. Separation of the metal parts, at least of the ferrous metals, presents difficulty particularly when these parts are supplied to the pulverizing machine in filled refuse sacks, cartons or bundles. The over-belt magnets and other magnetic separating devices which have been used in the past are scarcely capable of separating iron parts which are present in refuse bags, sacks, cartons and the like.